Tool safety device



o U mted States Patent 1 3,543,621

1 "21 Inventor John H. Wetland [56] References Cited Bronxville, New York UNITED STATES PATENTS P 7371201 9 1,375,924 4/1921 McDonald 83/62X I221 PM m 2,134,933 11/1938 Smith 72/3 1451 A 2,589,849 3/1952 Oetiker 83/61 [731 Ass'gnee 3,440,909 4/1969 Schmid m1. 83/61 Romanshorn, Switzerland I b mesne assignments Primary Examiner-James M. Meister Att0rneyCraig, Antonelli, Stewart & Hill [54] TOOL SAFETY DEVICE 24 Claims, 2 Drawing Figs.

[52] US. Cl 83/61, ABSTRACT: A tool safety device in which a tool support is 83/522, 83/690 floatingly supported with respect to the frame, and in which [5 1] Int. Cl. 826d 5/00, the continued presence of a workpiece from a previous opera- B26f 1/14 tion or the failure of the workpiece ejection mechanism is [50] Field of Search 83/58, 61, sensed by such relative movement to close a control'circuit that stops the punch press or the like.

' Patented Dec. 1,1970- Sheet Z. of 2 INVENTOR. JOHN H. WEILAND ATTORNEYS TOOL SAFETY DEVICE BACKGROUND OF THE INVENTION The present inventionrelates to a tool safety device for use with punch presses or similar machines, and more particularly to a tool safety device which stops the punch press or causes the die to open in case of malfunction of the ejection mechanism or in case of excessive resistance offered by the workpiece at a given position prior to the actual punching operation.

Tool safety devices of the aforementioned type are known as such in the prior art.

In one prior art tool safety device, a mechanical linkage system is used to actuate a brake and clutch mechanism when a jam occurs, tending to obstruct the movement of the male die or when a jam occurs, interfering with the operation of the ejecting mechanism or when a jam occurs in the feedway. However, this type of prior art utilizes complicated mechanical linkages that are not only relatively expensive but poorly suited for high-speed operations.

Another prior art safety device for a punching machine utilizes a lever system actuating a contact in case of failure of the ejection mechanism to stop the machine. This prior art device is also relatively complicated in its construction and requires accurate adjustment of the parts to assure proper operation.

Additionally, tool safety devices are known which utilize microswitches actuated by sensing device to stop the operation of the machine in case of malfunction or improper positioning of the workpieces. However, these prior art devices require special control circuits and are ill-suited to protect punch presses that operate with relatively large forces.

SUMMARY OF THE INVENTION- The present invention aims at a tool safety device which eliminates the aforementioned shortcomings and drawbacks encountered in the prior art and which is particularly suited for use with punch presses producing metal stampings or blanks. Additionally, the tool safety device of the present invention is adapted in a very easy manner to hydraulic presses which can be easily controlled or stopped.

The present invention essentially consists of a floating support element supporting one part of the die which is displaced in the direction toward a first microswitch during closing of the die by an actuating ram, preferably a hydraulically actuated ram, whereby the-first microswitch is arranged in a control circuit in such a manner that during normal operation, it closes only after a second microswitch in series therewith, which is normally closed during the closing movement of the actuating ram, opens shortly before the closing of the first microswitch, provided the previously punched-out part has been ejected properly and the new workpiece is in proper position. On the other hand, in the event of malfunctioning of the ejection mechanism or improper positioning of the workpiece, the first microswitch is actuated by the floating support member before the second microswitch is opened so that closure of the two series-connected switches stops the machine or reverses the movement of the ram in the opening direction until it completely opens the die again where it is stopped.

Accordingly, it 'isan object of the present invention to provide a safety device for machine tools which eliminates by simple means the aforementioned shortcomings and drawbacks encountered in the prior art.

Another object of the present invention resides in a safety device for machine tools such as punch presses or the like which prevents damage to the die or punch'in an extremely reliable and simple manner in case a part or slug is not properly ejected or a malfunctioning occurs.

A further object of the present invention resides in a safety device for machine tools which is not only simple in construction but lends itself to ready adaptation for hydraulic presses and the like without involving costly parts orrequiring extensive redesigns.

Still a further object of the present invention resides in a safety device which utilizes relative movement between a floatingly supported die and the fixed frame to control the operation of the machine in case of malfunction.

Still another object of the present invention resides in a safety device for machine tools which utilizes simple control parts such as commercially available microswitches to provide the added safety control features described above.

These and further objects, features, and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing, which shows, for purposes of illustration only, one embodiment in accordance with the present invention, and wherein:

FIG. 1 is a schematic wiring diagram of a part of the control circuit for a conventional hydraulically operated punch press with a tool safety device in accordance with the present invention; and

FIG. 2 is a partial cross-sectional view through a conventional. hydraulic punch press equipped with a tool safety device according to the present invention.

Since the control mechanism for a hydraulic punch press is conventional and well known, forming no part of the present invention, only those parts thereof are illustrated in FIG. 1 which are related to the present invention.

Referring now to the drawing wherein like reference numerals are used throughout the two views to designate like parts, and more particularly to the partial wiring diagram for the tool safety device in FIG. 1, reference numerals 100 and 101 designate therein supply lines for the control voltage, normally an ac. line voltage. Connected in parallel with the lines 100 and 101 are the branch lines 100a and 1010. A second branch line 1001) is connected in parallel with the line 100a and includes a first microswitch generally designated by reference numeral 10 and a second microswitch generally designated by reference numeral 4 connected in series with the microswitch 10. A further branch line 100a which includes a third microswitch generally designated by reference numeral 5 is connected with the line 10% in such a manner that the two microswitches 4 and 5 are-in effect in parallel with each other and each microswitch 4 or 5 is in series with the microswitch 10.

The control winding of the relay generally designated by reference numeral 131 is connected between lines 101a and 10011. The control relay 131 includes a contact 131 that closes a holding circuit between the lines a and 10%. A second control relay generally designated by reference numeral 113 has its control winding connected in parallel with the control winding of relay 131 by way of lines 10% and 101b. A warning light is also connected across lines 10% and 101b to indicate when relays 131 and 113 are energized. The control relay 113 includes a movable contact 113 which, upon energization of this relay closes a control circuit 300, 300a, 301a and 301. The contact 113 is in parallel with the push button generally designated by reference numeral 111 and forming the'conventional control button for the UP and STOP control of conventional construction for the hydraulically actuated ram.

The control winding of relay 130 is connected between lines 101a and 100C and upon energization closes its holding contact 130', establishing a connection between line 100a and 100c. The control winding of the control relay generally designated by reference numeral 114 is connected in parallel by way of lines 1000 and 101c with the control winding of relay 130 and, upon energization, closes its contact 114' to close the control circuit 200, 200a, 201a and 201. The contact 114' is, in effect, in parallel with the STOP" control button generally designated by reference numeral 112 which is arranged in the conventional stop circuit for the hydraulic ram.- A warning light is also connected across lines 100c and 101a to indicate when relays 130 and 114 are energized. As mentioned above, the control mechanism for the ram is conventional and well known in the art, utilizing electrically conyoke 15 trolled valves or the like, and a detailed description is therefore dispensed with herein since it forms no part of the present invention, the push buttons 111 and 112 controlling conventional energizing circuits for solenoid valves directing hydraulic fluid to the ram and return cylinder. The operation of the control circuit illustrated in FIG. 1, insofar as it relates to'the present invention, will be described more fully hereinafter.

Referring now to FIG. 2 of the drawing, reference numeral 15 designates therein a rigid stationary frame structure of any conventional construction which carries a fixed bolster .plate 16 suitably secured thereto. The movable ram generally designated by reference numeral 60, which is also of conventional construction and therefore indicated only schematically, moves within the area of upper part 15 of the stationary frame. A cam 22 is appropriately secured by means of a bracket or yoke 61 and a rod 62 in such a manner as to move in unison during the reciprocating movements of the ram 60. The cam 22 engages with the microswitch 10, which in turn is adjustably mounted by conventional means on the upper frame part For this purpose, an upright member 71 is used which includes a support 72 along which the microswitch 10 is adapted to slide and to which the microswitch 10 can be suitably clamped in any position by a conventional clamping mechanism 73.

The fixed bolster plate 16 carries a floating die-support table generally designated by reference numeral 80 which is guided by means of guide pins 19 sliding in conventional antifriction guides 20. A suitable number of guide pins 19 sliding in antifriction guides 20 may be provided and may be spaced in any suitable manner about the floating table 80. The table 80 carries the lower die shoe 81 while the upper die shoe 81 is secured to ram 60. A counterpressure cylinder 82 is secured by appropriate means, for example, bolts 83 to the floating table 80 to move in unison therewith. A hydraulic piston 84 is adapted to reciprocate within the cylinder 82 and is connected by way of yoke 26 with the spring-loaded switch-actuating pin 25. The table 80 is normally biased upwardly by the counterpressure cylinder 82 which contains the piston 84 whose purpose is to push the blanked workpiece or slug upwardly, whence it is ejected by an air stream in a conventional manner. The valving or hydraulic circuit for cylinder 82 is not shown since it forms part of a conventional control used with a customary, known hydraulic ejecting mechanism. The floating table 80 can move vertically only a very short distance in its downward movement since shoulder 16' in bolster plate 16 forms an abutment against which the floating table 80 will come to a stop after traversing this small distance.

An air cylinder generally designated by reference numeral 90 is secured to the stationary frame 15 by way of bracket or and exerts a biasing force in the upward direction on the movable table 80. The pressure of the air cylinder 90 is controlled in a conventional manner by a three-way solenoid valve 23'which normally provides a higher pressure, for example, of about 40 psi to move the table 80 into its upper position. However, the moment the upper ram 60 is on the downstroke, this higher pressure is reduced by the solenoid valve 23 to approximately 12 p.s.i. in order to enable downward movement of the floating table 80 with a minimum of applied pressure. The control of the three-way solenoid valve is achieved in any conventional manner, known per se in the prior art and therefore not illustrated in detail herein.

The microswitch generally designated by reference numeral 4 is secured to the yoke 15" by means of bracket 51 while the microswitch generally designated by reference numeral 5 is connected with the cylinder 82 by means of bracket 52. The microswitch 4 is directly actuated by the bottom surface of the cylinder 82 while the microswitch 5 is actuated by an actuating rod 25 connected to the yoke 26, itself connected with the piston 84 sliding within cylinder 82. The control rod 25 and therewith the yoke 26 are normally biased downwardly by a spring 27 to close the microswitch 5.

OPERATION During normal operation when the ram 60 descends, cam 22 moves in unison therewith and keeps the microswitch 10 closed before the die is engaged, i.e., upper die shoe 81' engages the lower die shoe 81. Engagement of the upper and lower die shoes 81' and 81 causes the floating table to move downwardly. The initial movement of table 80 actuates the microswitch 4 to close the latter. However, the microswitch 10 is so adjusted in its position on the support 72 relative to cam 22 that it is normally opened just before switch 4 is closed. The floating table 80 then descends a short distance to come to rest on stop 16' to become in effect a stationary part of frame 15. The punching or shearing of the blank from the working stock between the die shoes 81 and 81 depresses the ejector 24 to which hydraulic piston 84 is attached. As mentioned previously, yoke 26 is biased downwardly by spring 27 to tend to close microswitch 5. Consequently, as the ejector 24 has descended, it has permitted yoke 26 and pin 25 to descend so that previously open switch 5 is now closed.

Referring to the wiring diagram of FIG. 1, closing of switch 5 does not close the series circuit b, 1000 because switch 10 is now open in normal operation.

When the ram 60 retracts upwardly, the hydraulic pressure in cylinder 82 acting on piston 84 forces ejector 24 upwardly to eject the blank. This opens microswitch 5 before switch 10 is closed again. After ejection of the blank, the latter is blown out of the way by an air jet as is common practice in conventional presses.

However, if the ejector fails to eject the blank, switch 5 would remain closed, and after the ram 60 has ascended a sufficient distance to close switch 10, the series circuit 100b, 100C would be closed to energize relays and 114 to thereby close the regular, conventional control circuit 200, 200a, 201a, 201 of the press to stop the press and turn on the warning light 160. Relay 130 acts in the manner of a latching or self-holding relay since it remains closed due to the closure of contact 130 which provides a parallel energizing path 100a, 101a for its energizing coil even though the microswitch 5 and/or 10 are opened again later on. It is therefore necessary to restore the relay 130 to the release position either manually or by breaking the circuit with a conventional additional manually operated pushbutton switch that can be placed into the energizing circuit for the winding of relay 130.

In operation, assuming that a part or slug is not removed and ram 60 descends for another stamping cycle, the obstruction causes the floating table 80 to descend earlier and close microswitch 4 before cam 22 has permitted microswitch 10 to open. Consequently, the series circuit 1110b is closed to energize the control winding of relay 131 and causes relay switch 113 to close the regular control circuit to cause the ram 60 to return to the upper position and stop. This circuit can also be closed by the regular control button 111 which is part of the conventional hydraulic press and controls a solenoid valve,

also part of the conventional system. Relay 131 is of the same construction as relay 130 and thus its operation is similar to that described for relay 130.

While I have shown and described only one embodiment in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to a person skilled in the art, and I therefore do not wish to be limited to the details shown and described herein but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

I claim:

1. A safety device for machines such as punch presses and the like producing a workpiece during the normal cycle of operation involving closing and opening a die, which includes a relatively fixed frame structure, an actuating mechanism for effectively closing and opening the die and an ejection mechanism for ejecting the workpiece from the die, wherein the improvement comprises die-support means, means for floatingly supporting said die-support means on said relatively fixed frame structure to provide during normal operation predetermined movements of said die-support means relative to said frame structure near the end of the die-closing movement and the beginning of the die-opening movement, and control means for interrupting the normal cycle of operation of the die by said actuating mechanism in response to movement of said die-support means different from said predetermined movements.

2 A safety device according to claim 1, wherein said control means includes first means for detecting the continued presence of a workpiece in the die during die-reclosing movement of the actuating mechanism.

3. A safety device according to claim 2, wherein said control means includes second means for detecting malfunction of the ejection mechanism.

4. A safety device according to claim 3, wherein said control means includes an electric control circuit having a first microswitch actuated by said actuating mechanism and two further microswitches both in series with said first microswitch and connected in parallel to each other to provide in effect two series circuits each including the first microswitch and a respective further microswitch, and electrically operated means operable to interrupt the normal cycle of operation upon closing of a respective series circuit.

5. A safety device according to claim 4, wherein one of said further microswitches is closed by downward movement of the die-support means and the other further microswitch is normally closed and is opened only during movement by a part of the ejecting mechanism indicating ejection of the workpiece.

6. A safety device according to claim 5, wherein the electrically operated means includes relay means energized by closing of a respective series circuit and provided with holding contact means.

7. A safety device according to claim 6, wherein said control means returns the actuating mechanism to and stops the same in the position corresponding to the fully opened die position upon closing of the series circuit including the second means.

8. A safety device according to claim 7, wherein said control means stops the actuating mechanism upon closing of the series circuit including said first means.

9. A safety device according to claim 8, wherein said means floatingly supporting said die-support means relative to said frame structure includes pneumatic means normally providing a first relatively larger force to move said die-support means away from said frame structure and a second relatively smaller force during at least a substantial part of the die-closing movement of said actuating mechanism. I

10. A safety device according to claim 9, wherein said actuating mechanism includes a hydraulically actuated ram.

11. A safety device according to claim 4, wherein the electrically operated means includes relay means energized by closing of a respective series circuit and provided with holding contact means.

12. A safety device according to claim 1, wherein said control means returns the actuating mechanism to and stops the same in the position corresponding to the fully opened die position.

13. A safety device according to claim 1, wherein said control means stops the actuating mechanism.

means floatingly supporting said die-support means relative to said frame structure includes pneumatic means normally providing a first relatively larger force to move said die-support means away from said frame structure and a second relatively smaller force during at least a substantial part of the dieclosing movement of said actuating mechanism.

15. A safety device according to claim ll, wherein said actuaitisnamechanism includes a hydraulicall actuated ram.

safety device according to claim wherein said control means includes means for detecting malfunction of the ejection mechanism.

17. A safety device according to claim ll, wherein said control means includes an electric control circuit having a first microswitch actuated by said actuating mechanism and two further microswitches both in series with said first microswitch and connected in parallel to each other to provide in effect two series circuits each including the first microswitch and a respective further microswitch, and electrically operated means operable to interrupt the normal cycle of operation upon closing of a respective series circuit.

18. A safety device according to claim 17, wherein one of said further microswitches is closed by downward movement of the die-support means and the other further microswitch is normally closed and is opened only during movement by a part of the ejecting mechanism indicating ejection of the workpiece.

19. A safety device according to claim 17, wherein the electrically operated means includes relay means energized by closing of a respective series circuit and provided with holding contact means.

20. A safety device for machines such as punch presses and the like producing a workpiece during the normal cycle of operation which includes a relatively fixed frame structure, an actuating mechanism for effectively closing and opening a die and an ejection mechanism for ejecting the workpiece from the die, wherein the improvement comprises die-support means, means for floatingly supporting said die-support means on said relatively fixed frame structure to enable during normal operation a predetermined small movement of said diesupport means relative to said frame structure near the end of the die-closing movement, and control means for sensing the improper presence of a workpiece by the relative movement of said die-support means and for thereupon interrupting the normal cycle of operation by said actuating mechanism.

21. A safety device according to claim 20, wherein said control means includes an electric control circuit having two series connected microswitches, and electrically operated means operable to interrupt the normal cycle of operation upon closing of the respective series circuit.

22. A safety device according to claim 21, wherein one of said microswitches is closed by downward movement of the die-support means.

23. A safety device according to claim 21, wherein one of said microswitches is normally closed and is opened only upon ejection of the workpiece. 24. A safety device according to claim 21, wherein the electrically operated means includes relay means energized by closing of the respective series circuit and provided with holding contact means. 

